A traditional platform for an elevator car is comprised of a steel plate or sheet over a plurality of steel stringers. The steel plate provides a smooth surface for the floor and the steel stringers provide a rigid structure. Although such a configuration is sufficient for most purposes, it suffers from the drawback of being very heavy and expensive to fabricate.
Of more recent development are honeycomb platforms. These are typically a honeycomb core material sandwiched between two thin sheets of metal and a top layer of some form of structural material. The additional top layer of material is necessary to provide structure to anchor cab components to, such as a car door threshold. The honeycomb layer alone, unfortunately, tends to buckle under the compressive forces of a typical through-bolt fastener for the threshold or other component. Another drawback to this type of platform is the thickness of the honeycomb layer required to carry the operational loads. A thick platform necessitates a larger car frame.
Another recent development is the use of wood composite platforms. An example of this type of platform is disclosed in U.S. Pat. No. 4,848,519, entitled "Structural Support for Hydraulic Elevator Car" and issued to Ericson et al. The platform disclosed therein is comprised of a floor portion formed from wood, composite or oriented strand wood fiber material and a metallic lower plate functioning as a fire stop. The support frame for the platform includes a planar array of tubular beams disposed widthwise relative to the elevator. This configuration reduces the weight of the platform as compared to traditional types of platforms.
In addition to weight, a further consideration is the noise level within the elevator cab. The elevator cab is subjected to numerous sources of vibration and acoustic energy, such as the operation of the doors. The doors are typically hung from a door frame attached to the cab and actuated by a motor unit disposed on the elevator car. Operation of the doors produces vibration energy that may be transmitted into the cab and which is disturbing to the passengers within the cab. The conventional solution to this is to sound isolate the doors from the cab by providing a sound isolation frame under the platform assembly and extending the door frame from the sound isolation frame and the car frame. In effect, the doors and door frame are separate from the cab. Sound isolation pads are placed between the sound isolation frame and the platform assembly and between the car frame and the platform assembly. The additional sound isolation frame, however, adds to the weight and cost of the elevator.
The above art notwithstanding, engineers and scientists under the direction of Applicant's assignee are working to develop lightweight, durable elevator car frames and platform assemblies that result in a quiet and comfortable ride for the elevator passengers.